Solve 4x − 9 = −1

The solution of 4x − 9 = −1 is x = 2.

4x - 9 = -1\ \Rightarrow\ x = 2

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The lines y = 4x − 9 and y = -1 meet at x = 2. The solution of the equation is the x-coordinate of the point where the two sides are equal.

How to work it out

1
The goal is to get x alone. Undo the operations in the opposite order: first the subtraction, then the multiplication.
$4x - 9 = -1$
2
Add 9 to both sides:
$4x - 9 + 9 = -1 + 9 \ \Rightarrow\ 4x = 8$
3
Divide both sides by 4:
$\frac{4x}{4} = \frac{8}{4} \ \Rightarrow\ x = 2$
4
Check: put x = 2 back into the equation.
$4\cdot2 - 9 = 8 - 9 = -1 \checkmark$

LaTeX source of the formulas on this page

\[ 4x - 9 = -1\ \Rightarrow\ x = 2 \]
\[ 4x - 9 = -1 \]
\[ 4x - 9 + 9 = -1 + 9 \ \Rightarrow\ 4x = 8 \]
\[ \frac{4x}{4} = \frac{8}{4} \ \Rightarrow\ x = 2 \]
\[ 4\cdot2 - 9 = 8 - 9 = -1 \checkmark \]

Trying values of x in 4x − 9 = −1

x	4x − 9	Equals -1?
0	-9	no
1	-5	no
2	-1	yes
3	3	no
4	7	no

Questions

What is x in 4x − 9 = −1?

The solution of 4x − 9 = −1 is x = 2.

How do you solve 4x − 9 = −1?

Add 9 to both sides to get 4x = 8, then divide both sides by 4 to get x = 2.

How do I check the answer?

Replace x by 2: 4(2) − 9 = -1, which is -1.

Solve 4x − 9 = −1

How to work it out

Trying values of x in 4x − 9 = −1

Questions

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